Episode 6

The search for H reaches its climax in a ninety-minute finale, and Hastings's secrets are finally laid bare. The episode is built around the question the whole season has been circling, and the reveal, when it comes, is delivered with the show's usual care for the long game. The length of the episode is a gift. Ninety minutes is a long time to hold a room, and the show uses every one of them.

There is room for the tension to build properly, and for the revelations to land one at a time instead of in a heap. The focus narrows onto Hastings as his accumulated secrets are exposed, and the episode manages the trick of making the institutional personal. Around him, the team is caught between duty and loyalty, and the cost of the truth is counted in careers. The pace is relentless, but the show never lets the hour become a blur. The interrogations are long, and the silences between answers do the real work. Every thread from the season is pulled through the same needle, and the episode keeps them straight.

Jed Mercurio wrote it, Susan Tully directed. Adrian Dunbar carries the finale, and Anna Maxwell Martin's Carmichael brings a new and chilly energy to the proceedings. Martin Compston's Arnott, Vicky McClure's Fleming, Polly Walker's Biggaloe, Natalie Gavin's Tranter, Laura Elphinstone's Brandyce, Taj Atwal's Sohota, Ace Bhatti's Sindwhani and Elizabeth Rider's Wise complete the cast. It is a finale-sized cast, and everyone gets a moment that matters.

There is a particular satisfaction in a finale that has earned its reveals, and this one has. The secrets come out the way secrets usually do: messily, and at a cost. But the identity of H is the destination, and the journey has been long enough to make it matter. The reveal is worth the wait, and the wait has been considerable. The episode works as both a thriller and a reckoning, and it does not let one crowd out the other. The truth is out, and the truth has a price tag.